1. Field of the Invention
The present invention relates to triphenylene compounds useful, for example, in an electrophotographic photoreceptor, and to a method for manufacturing these compounds.
2. Discussion of the Background
Recently, information-processing systems using electrophotographic methods are making a remarkable progress. In particular, laser printers and digital copiers which record data with light by changing the data into digital signals make remarkable improvements in their printing qualities and reliabilities. Further, technologies used in these printers and copiers are applied to laser printers and digital copiers capable of printing full-color images with high-speed printing technologies. Because of these reasons, photoreceptors are required both to produce high-quality images and to have high durability.
Photoreceptors using organic photosensitive materials are widely used for these laser printers and digital copiers due to their cost, productivity and non-polluting properties. The organic photoreceptors are generally classified to a single-layered type and a functionally-separated type. The first practical organic photoreceptor, i.e., PVK-TNF charge transfer complex photoreceptor was the former single-layered type. In 1968, Mr. Hayashi and Mr. Regensburger independently invented PVK/a-Se multi-layered photoreceptor. In 1977, Mr. Melz, and in 1978, Mr. Schlosser disclosed a multi-layered photoreceptor whose photosensitive layers are all formed from organic materials, i.e., inorganic-pigment dispersed layer and an organic low-molecular-weight material dispersed polymer layer. These are called as functionally-separated photoreceptors because of having a charge generation layer (CGL). generating a charge by absorbing light and a charge transport layer (CTL), transporting the charge and neutralizing the charge on a surface of the photoreceptor. The multi-layered photoreceptor has much more improved sensitivity and durability than the single-layered photoreceptor. In addition, since materials can be separately selected for a charge generation material (CGM) and a charge transport material (CTM), a choice range of the materials is largely expanded. Because of these reasons, the multi-layered photoreceptor is now prevailing in the market.
A mechanism to form an electrostatic latent image in the multi-layered photoreceptor is as follows:                the photoreceptor is charged and irradiated with light;        the light passes through the CTL and is absorbed by the CGM in the CGL to generate a charge; the charge is injected into the CTL at an interface of the CGL and the CTL; and        the charge moves in the CTL by an electric field and neutralizes the charge on the surface of the photoreceptor to form an electrostatic latent image.        
Recently, in accordance with speeding up of the printing speed and downsizing of an image forming apparatus, the photoreceptor has to have a smaller diameter, so rapid response and stability thereof become a more important subject.
The following are commercially available charge transport materials that are conventionally known:    1,1-bis(p-diethylaminophenyl)-4,4-diphenyl-1,3-butadiene (Japanese Laid-Open Patent Application 62-30255), 5-[4-(N,N-di-p-tolylamino)amino)benzylidine]-5H-dibenzo[a,b]cycloheptene (Japanese Laid-Open Patent Application 63-225660), 9-methylcarbazole-3-aldehyde1,1-diphenyl, pyrene-1-aldehyde1,1-hydrazone, diphenylhydrazone (Japanese Laid-Open Patent Application 58-159536). 4′-bis(4-methylphenyl)amino-α-phenylstilbene, N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine, and 9,9-dimethyl-2-(di-p-tolylamino)fluorene.
The charge transport layer is generally a film with a thickness of about 10 to 30 μm made from a solid solution in which a low-molecular weight charge transport material is dispersed in a binder resin. Most of the currently available photoconductors employ as a binder resin for the charge transport layer a bisphenol polycarbonate resin or a copolymer consisting of a monomer of the above-mentioned polycarbonate resin and any other monomers. However those charge transport material are not sufficient to satisfy rapid response to the process speed of the future.
On the contrary, molecular design about those charge transport material of rapid response(high mobility) are tabulated in the Society of Electrophotography of Japan, 25 (3), 16 (1986). In other words phenylamine group (>N-phenyl) as a functional group, the number of phenylamine group (>N-phenyl) are related to high mobility clearly.
Present compound which have multifunctional group bring rapid response to pass on this basis.